Despite having one of the smallest majorities in the country, he has spent much of his short career in Parliament bidding for the leadership of his party.

He ran Sir Menzies Campbell a good second in last year's contest - triggered by ousting of Charles Kennedy - with 42% of the votes compared with Sir Menzies' 58%.

He robustly denied the suggestion that he originally agreed not to stand against Sir Menzies, only to then renege on the deal.

He seized the opportunities handed him by Sir Menzies, who made him environment spokesman - one of the most high-profile in the party and central to its appeal.

He has pushed through new green policies in the face of a concerted bid by the Tories to fence off that ground as their own.

'Personal' campaign

He was the first to declare his candidacy when Sir Menzies shocked Westminster by announcing he was standing down.

He started as an outsider to the younger, and arguably more telegenic, Nick Clegg, with much less support among MPs and party grandees.

But the contacts he made during the 2006 leadership campaign - as he travelled the country drumming up grassroots support - undoubtedly gave him a head start.

And he ran a vigorous, even aggressive, campaign, putting Mr Clegg on the back foot over issues such as Trident nuclear missiles.

There were also suggestions Mr Huhne's campaign got a little "personal" in its criticisms of his rival.

A briefing note entitled "Calamity Clegg" was put down to an "over-zealous researcher".

Mr Huhne apologised over the incident but continued to accuse Mr Clegg of "flip-flopping" on issues like the NHS and education.

Millionnaire

He also skillfully manouvred himself into the headlines over issues far beyond his policy brief, such as the Labour "proxy" donations row.

Like Mr Clegg, the 53-year-old was educated at Westminster school, worked as a journalist and then a member of the European parliament before becoming an MP in 2005.

He is thought to be a millionnaire several times over but has always been reluctant to talk about his investments, which are reported to include - until last year - a stake in an Egyptian gold mine.

Mr Huhne's mother was the actress Ann Murray, who had a stage and film career in the 1950s.

His wife, Vicky Pryce, is chief economist at the Department for Business, Enterprise and Regulatory Reform. The couple own seven houses, five of which are let out as rental properties. Huhne has three children and two stepchildren.

'Revolting' student

His radical past came under scrutiny during the leadership campaign, including an article he wrote at Oxford, which appeared to advocate the use of LSD and other hard drugs.

He was also pictured during a demonstration brandishing a park bench as other students smashed their way into a building.

Mr Huhne, who was reportedly known as Christopher Paul-Huhne at Oxford, where he gained a first in Politics, Philosophy and Economics, laughed off such revelations by saying he was a "revolting student" in every sense of the word.

He is seen as being to the left of Mr Clegg, although, in reality, there are precious few policy differences between them.

He is the author of four books, including titles on debt and the developing nations, and on European integration.